The invention relates to a self-energizing disc brake.
Self-energizing brakes—also with an electromechanical actuator—are known in various embodiments. The majority of the known brakes, however, describe operating principles which, although they permit self-energizing, are unsuitable for realizing a production-ready, economically producible, disc brake for heavy utility vehicles, particularly on account of their cumbersome structural design.
It is therefore a basic problem with self-energizing disc brakes for utility vehicles trying to realize an efficient radial stabilization, in particular of the application-side brake pad in a structurally simple manner. Since the two pressure spindles of utility vehicle brakes are arranged offset with respect to one another in the peripheral direction or tangentially, the arrangement is efficiently stabilized against peripheral oblique wear. In the radial direction with respect to the brake disc rotational axis, however, there is no aligning action or at least only a very small amount of aligning action. In particular, when using balls as rolling bodies between the application-side brake pad and the pressure spindles, it is conceivable for the brake pad to begin to oscillate, at least in the event of non-optimum alignment, in the non-actuated state of the brake, which can cause said brake pad to constantly run against the brake disc, which can in turn result in undefined wear of the pad and/or disc.
In the same way, radial oblique wear, which is generated during braking processes can progress unhindered. The result is early wear of the brake pad, which can entail unnecessarily high service costs and vehicle down-time periods, in particular where the disc brake is designed for heavy utility or commercial vehicles.
For this reason, in order to generate a sufficient alignment action, it has already been proposed in the prior art to provide further application points in a disc brake in addition to the long-known arrangement of two application points or pressure spindles (such an arrangement is already known per se for example, from pneumatically actuated disc brakes). Such a proposal is disclosed, for example, in DE 103 36 284 A1.
In commercial vehicle brakes, however, the arrangement for example of a third pressure spindle is very complex on account of the necessary wear adjustment and also cannot be realized, or can be realized only with difficulty, due to space constraints.
Against this background, the present invention seeks to obtain efficient radial stabilization of the application-side brake pad for self-energizing disc brakes using structurally simple measures.
According to the invention, the two pressure spindles or brake plungers are connected to one another via a connecting plate, with at least one or more ramp arrangements being formed in the region adjacent to the brake plungers between the brake pad, or a brake pad unit composed of a brake pad and an additional pressure plate, and the connecting plate.
Pad lining stabilization in the radial direction too can be obtained in a simple manner by way of the at least one or more ramp arrangements, as an extension of the brake plunger, between the brake pad (or a brake pad unit which comprises the brake pad and, if appropriate, a pressure plate or the like) and the connecting plate.
Here, in each case, one ramp/rolling-body arrangement is particularly preferably also formed between the brake plungers and the brake pad unit. Each of the pressure surfaces of the at least two or more brake plungers is particularly preferably also provided on its side facing toward the brake pad unit with a recess having a ramp-shaped contour into which engages, in each case, one rolling body which is supported at one side against the ramp-shaped contour of the pressure surfaces of the brake plunger and at the other side against the brake pad unit.
The ramp/rolling-body arrangements between the brake plungers and the brake lining unit serve to transmit and support the brake force. The ramp/rolling-body arrangements are, therefore, referred to below as “primary ramp/rolling-body arrangements”.
In contrast, the ramp arrangements between the brake pad and the connecting plate are referred to as “secondary ramp/rolling-body arrangements”.
By means of the “primary ramp/rolling-body arrangements”, the self-energizing brake is combined in a simple manner with an adjusting device. The application of the brake in the direction of the brake disc (or perpendicularly with respect to the brake disc) takes place by way of the brake plunger by virtue of the length of the latter being varied axially. The application in the peripheral direction or parallel to the disc takes place in a different way, for example way by way of a crank. The brake plungers can also be co-utilized for adjusting brake pad wear. There are, advantageously, an extremely wide variety of options during braking operations, which are explained in more detail below.
It is expedient if the connecting plate is composed of a metal plate. Other materials are contemplated, since the connecting plate serves not to transmit the significant braking forces but rather to stabilize the arrangement.
It is expedient that the connecting plate has two openings for the two brake plungers, and that the connecting plate is fixed to the brake plungers in order to move synchronously with the latter parallel to the brake disc rotational axis during application and adjustment movements.
A further opening is preferably formed in the connecting plate, through which further opening extends an electromotively driven crank pin for moving the brake pad unit. Other types of drive for the brake pad unit are also possible. For example, a linear drive may be used with a substantially analogous arrangement. Here, instead of the crank pin, a gearwheel segment is placed onto the drive shaft, which gearwheel segment engages into a toothed rack on the lining rear side (not illustrated here). However, a non-linear drive is preferably used. Also possible are lever arrangements operating as an application device between the electric motor and the brake pad unit (not illustrated here).
The ramp arrangements particularly preferably have, in each case, one recess in the connecting plate and one corresponding recess in the brake pad unit, into which recess a rolling body engages.
Here, it is expedient if one or, in each case, both of the recesses in the connecting plate or brake pad have a ramp-shaped contour, which runs obliquely with respect to the brake disc friction surface. The self-energizing action can be realized by way of the ramp-shaped contours, which run obliquely with respect to the brake disc friction surface, in interaction with the ramps on the brake plungers, since the rolling bodies run on the plungers during braking. The significant forces are absorbed by the brake plunger. The ramps in the connecting plate have primarily a stabilizing effect.
It is expedient if one or, in each case, both of the recesses in the connecting plate or brake pad have a geometry which is matched to the rolling body geometry.
The rolling bodies between the connecting plate and the brake pad unit are preferably composed of metal. It is also contemplated for the rolling bodies to be composed of metal, ceramic, glass or plastic since the rolling bodies need absorb only low forces.
It is expedient if the recesses in the brake pad unit and/or in the connecting plate are formed as groove-shaped raceways.
For braking operations when traveling forward and when traveling backward, and for braking operations when parking, it is also advantageous if the recesses are embodied in the form of dual-direction ramps.
The adjustable ramp system can also be utilized in order to realize a reliable parking brake, which also automatically adjusts in the event of friction bodies shrinking as a result of cooling. A further significant advantage of the invention is, therefore, also to be considered that of a reliably operating parking brake without additional actuating components being necessary.
For this purpose, the ramp angle with the greatest degree of self-energizing must be dimensioned such that self-energizing is possible even with the lowest contemplated lining friction value.
The control of the electromechanical brake takes place in each case by way of one or more processor units on the brake, which processor units are, if appropriate, networked, or for example by way of a superordinate processor on the vehicle for one or more brakes.
If normal force regulation, for example, is carried out, which is not considered to be usable as sole regulation according to the prior art, it is advantageous that, for example by way of the support of the brake plunger on the brake caliper, the normal force can be determined very precisely (force parallel to the longitudinal axis of the brake plunger), for example by virtue of corresponding sensors being arranged on the brake plungers and/or adjoining elements.
In each case, one ramp arrangement is preferably likewise formed between the brake plungers and the brake lining unit.
Not only is it contemplated for the ramp arrangement to be embodied as a ramp/rolling-body arrangement, the ramp arrangement can also be embodied as a particularly cost-effective ramp/cam arrangement. Instead of the rolling body, the more cost-effective cam—for example an embossed portion of the connecting plate—then slides on a ramp.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.